Precision substrates of semiconductor wafers having a diameter of 300 mm are stored in a front open box type storage container. A storage container of this kind is comprised of a front open box type container body that stores a plurality of unillustrated precision substrates in alignment, a door element for detachably closing the open front of the container body in a sealing manner and a locking mechanism for locking and unlocking the door element fitted at the front of the container body, and is configured so as to be standardized conforming to SEMI E47.1. The door element is automatically opened and closed by a door opening/closing device of processing equipment having a standardized mechanical interface.
The locking mechanism includes: a rotary plate that is supported by the door element and rotated by the door opening/closing device of the processing equipment; a pair of advancing and retracting plates that linearly advance and retract toward the peripheral wall of the door element as this rotary plate rotates; and engagement pieces, which are provided at the front ends of the advancing and retracting plates and project from the peripheral wall of the door element and fit into recesses on the inner periphery of the front of the container body when the door element is locked and retract from the recesses of the container body into the door element when the door element is unlocked.
In the above, when the open front of the container body is confined by the door element, the door opening/closing device of processing equipment tightly presses and fits the door element to the open front of the container body, then, the door opening/closing device causes the rotary plate of the locking mechanism to rotate from without so as to advance each advancing and retracting plate from the interior of the door element toward the peripheral wall. With this advancement of each advancing and retracting plate, each engagement piece projects out of the peripheral wall and fits into the recess of the container body, thereby enclosing the front of the container body with the door element in a sealed state.
In a case where the advancing and retracting plate of the locking mechanism and its engagement piece are formed of an integrated single part, as the advancing and retracting plate makes simple linear motions, there is a fear that the advancing and retracting plate and its engagement piece may abrade the recess of the container body to produce particulates. To eliminate this problem, there has been a proposal (see patent document 1) in which the front end part of the advancing and retracting plate is greatly inclined at an acute angle toward the thickness direction (width direction) of the door element) after the plate has been advanced. There is also another proposal (see patent document 2) in which the advancing and retracting plate is formed of a plurality of parts and a separate engagement metal shaft is rotatably supported at the front end part of the advancing and retracting plate.
Patent document 1:
Japanese Patent Application Disclosure Hei-04 No. 505234
Patent document 2:
Japanese Patent Application Laid-open No. 2000-58633.